Can a laptop track accurately enough to allow an intercept?
It can track as accurately as the resolution of the ADS-B location inputs. All the laptop does is listen to the ADS-B broadcasts and display the location, elevation, and call-sign data sent in the broadcast.
I don't know if the same location data (GPS? and/or INS?) is used in TACAS.
I would guess the location and elevation data is at least as good as GPS data - i.e. a couple of tens of metres laterally and twice that vertically.